Drill arm for metal drilling machinery



Jul 14, 1931. A; E ROBINQSON ETAL 1,814,963

DRILL ARM EOR METAL DRILLING MACHINERY Filed 20, 1928 5 Sheets-Sheet l as I] O July 14, 1931. A. E. ROBINSON ET AL DRILL ARM EOR METAL DRILLING MACHINERY Filed Aug. 20, 1928 5 Sheets-Sheet 2 /NVEN7'OR5:

Jul 14, 1931.

DRILL ARM EOR METAL DRILLING MACHINERY Filed Aug. 20. 1928 5 sheetssheet {3 //VVEN 70/75:

A. E. ROBINSON Ei- AL 6 July 14, 1931. A E. ROBINSON ETAL DRILL ARM EOR METAL DRILLING MACHINERY Filed Aug. 20, 1928 5 Sheets-Sheet 4 ILiIL mi lllrll" NM I H /Nl/EN ToRs;

July 14, 1931. A. E. ROBINSON ET AL DRILL ARM EOR METAL DRILLING MACHINERY Filed Aug. 20, 1928 5 Sheets-$heet 5 lllll l lllll .1

and to anchor the respective ends of the tension-member to the cast metal drill-arm while the latter is in compressively stressee relation, for resisting yield in the drill-arm to the work stresses; and, further, to form the cast metal drill-arm in the manner stated, and to then provide the same with the guideways for the t-oolslide.

The invention will be further readily understood from the following description and claims, and from tl e drawings, in which latter:

Fig. 1 is a front elevation of an exemplifying drilling machine, partly broken away, embodying our invention.

Fig. 2 is an end elevation of the same.

Fig. 3 is a side elevation of a rough casting for a drill-arm embodying a selected form of our invention.

Fig. 4 is a plan view of the same.

Fig. 5 is an angular section of the same, taken on the line 5-5 of Fig. 3.

Fig. 6 is a cross-section of the same, taken on the line 6-6 of Fig. 3.

Fig. 7 is a side elevation of the drill-arm in finished condition.

Fig. 8 is a cross-section of the same, taken on the line 88 of Fig. 7.

Fig. 9 is a side elevation of a core for the casting of a drill-arm having the tension-bar imbedded therein.

Fig. 10 is a side elevation of a rough casting for a drill-arm showing a modification of our invention.

Fig. 11 is a plan view of the same.

Fig. 12 is an angular section of the same, taken on the line 1212 of Fig. 10.

Fig. 13 is a side elevation of the same in finished condition.

Fig. 14 is a side elevation of a further modification for the rough casting for the drillarm; and,

Fig. 15 is a plan view of the same.

The exemplified drilling machine co1nprises a base 21 including a work-support A stationary post 23 extends rigidly upwardly from the base, and has a rotatable sleeve or column 24-, hereinafter referred to as a column, rotatable about the post on usual bearings, and arranged to be clamped in adjusted positions to the post, by means of a usual split-bearing 25 at the bottom of the column and usual clamping means therefor.

A drill-arm 28 extends above the work-support, and is exemplified asshiftable so as to place the drill-arm in desired position radially with relation to the post. The drillarm is provided with a bearing 29 about the column, this hearing being preferably a splitbearing, arranged to be clamped in adjusted elevational positions to the column by suitable clamping means, as at 30. The split bearing and clamping means may be of usual or ordinary construction.

A drill-arm of this character is usually adjustable up and down on the column, when the split-bearing 29 is in unclamped relation, by a usual upright screw 33 extending lengthwise of the column, and a usual nut 31 on the drill-arm, of usual construction, one of these complemental members being arranged to be rotated for raising or lowering the drill-arm. hen the drill-arm has been adjusted to desired radial position and to the desired elevational position, respectively, the clamping means 26 and 30 are clamped, for fixing the column rigidly to the post and fixing the drill-ar1n rigidly to the column.

The drill-arm is provided with guideways 36, 37, 38, 39, 40, extending lengthwise thereof, along which a tool-slide l1, provided with complemental guides, is arranged to slide or to be shifted lengthwise of the drill-arm by suitable manual or power means, for positioning a usual tool, for instance a drill 4-2, in a rotatable drill-spindle 43 on the tool slide, at proper position with relation to the work, exemplified at 44:, on the work-support. The tool-slide is arranged to be clamped in adjusted positions to the drillarm, by usual means, and suitable and usual feeding means, operated either manually or by power, are arranged to feed the tool-spindle with relation to the work.

In modern machine tool practice the tool is required to operate rapidly on the work, and great strains are thereby exerted in a direction lengthwise of the tool-spindle away from the work, which must be resisted by the drill-arm, and great stresses are thus exerted upon the drill-arm. A'ny yielding in the drill-arm to such stresses results in inaccuracy in the work and in undue power requirements for rotating the tool.

It is the usual practice to make such drillarm of a casting of metal, usually so-called gray cast iron, and attempts have been made to strengthen the drill-arm by casting the same in various shapes, as hereinbefore explained. We have found all such attempts to be inadequate for obtainin the highest efiiciency and output in a machine of this character, and have conceived the idea of absorbing the natural resiliency in the cast metal of the arm, or of amplifying and supplementing the resistance of the cast metal of the arm, by the resistance of a tension member so placed as to resist the bending raising stresses upon the arm throughout the various positions of the drill-slide lengthwise or" the arm, and we have preferred to arrange said tension member slanting with relation to the guideways on the drill-arm, and have found such arrangement most ad vantageous for the further reason that a drill-arm is usually a long overhanging structure limited in height and cross-section owing to weight of the metal.

We prefer to provide a tension-member e 14ers which is of steel, and has great tensile strength, and great resistance to load stresses by the tool. It may be in-stanced, as an example, but not as a limitation, that the ultimate load resistance of cast iron in a drillarm as usually constructed, is twenty-two thousand pounds ultimate per square inch, and that its safe working load is six thousand pounds per square inch. A steel tension member such as we employ has preferably a safe load resistance of ninety thousand pounds or more per square inch of crosssection.

A cast metal drill-arm of the character mentioned as usually heretofore employed has an initial yield or spring in the metal tending toward inaccuracy in operation.

It is the object of our invention to absorb such initial resilience or spring, which we accomplish by exerting forces upon the cast metal drill-arm in directions preferably counter to the directions of forces upon the drill-arm in the operation of the tool upon the work, and setting or anchoring the drillarm in such assumed condition.

Referring now to Figs. 3 to 6 inclusive, the cast metal drill-arm is exemplified at 51. Its interior is provided with a core-hollow 52, ribs 53 extending inwardly from the outer walls of the drill-arm, openings 54 being in the ribs. A tension-member 55 is anchored at 56 at one of its ends, at one end 57 of the drill-arm, being preferably anchored at one corner 58 of the drill-arm.

This anchoring is formed by imbedding the tension-member in the core 59 for forming the cavities in the drill-arm, one end of said tension-member, provided with annular grooves 60, projecting out of said core, and being imbedded in the cast metal of the drill-arm when the drill-arniis cast. The tension-member is diagonally arranged in said core for producing the result instanced.

The tension member is provided with a reduced end 61, the outer end of which is screw-threaded, as shown at 62. A bushing 63, provided with an annular flange 64 at its outer end, is received about this reduced end and in the bore 65 left by the core. A nut 66 is threaded over the outer threaded end of the tension-member, and is resisted by the end face 67 of said bushing, which end face is in a plane preferably perpendicular to the axis of the tension-member. The bushing 63 may be on the core. The flange 64 is resisted by the casting.

The casting may be provided with guideway formation 36, 37), 38, 39 and i0, which, when finished, become the guideways cc. 3.7, as, 39-and 40.

The casting may also be formed with a formation 29 which, when finished and provided with suitable slits and clamping means, becomes the clamp bearing 29 for the arm about the column.

Strains are new applied to the cast metal drill-arm for absorbing the initial yield or spring in the same, to produce a dead resisting mass for resisting the strains of the tool. This may be accomplished by bending or compressi estresscs applied to the drillarm, or by drawing upon the nut 66, for exerting tension stresses upon the tension-bar 55 and compressive stresses upon the cast metal drillarm, for absorbing such initial upward yield or spring of the cast metal-drill-arm. These stresses may be applied to flex the outer end of the arm downwardly with relation to its inner end.

It may be desirable for operative or constructive reasons in-finis'hing or use of the drill-arm, that the parts extending from the cast metal end of the drill-arm shall be re moved, which case we prefer to provide substitute anchoring means for the outer end of the tension member, for instance, in the form of pins 68, received through mating holes in the cast metal drill-arm and complementatl hole sectors in the extension 61 and the bushing 63, for securely anchoring the tension-member and the outer end of the cast metal drill-arm together.

The anchoring means between the outer end of the tension-member and the outer end 69 of the drill-arm, are preferably located in the corner 70 of the drill-arm, diagonally 0r obliquely opposite to the corner 58 of the drill-arm at which the opposite or inner end of the tension-member is anchored.

After such substitute anchoring of the outer end of the tension-member, the nut 66 may be removed, and the outer ends of the tension-member and of the bushing projecting beyond the outer end of the cast metal drill-arm may be removed in suitable manner, as by planing,'shaping or milling, and the remaining surface finished to present a straight and unbroken end surface for the drill-arm.

It may be stated as an exemplification, but not as-a limitation, that the cross-sectional area of the tension-member may be three and three-quarter inches, andin the proportion shown in the drawings with relation to the cross-sectional area of the casting, and that the tension-member may be a steel bar, for instance of alloy steel having very high tensile strength, for instance, an alloy steel containing chemical cleansing ingredient, such as manganese, nickel or vanadium, to produce a steel having avery dense fibre. The tensile strength of such steel is as high as one hundred and seventy-five thousand pounds per square inch of cross-section of the bar. The bar is preferably a flat bar with its width dimension extending in upright direction. The bolts and nuts for the bars are preferably of the same material as the material of the bar. r

In Figs. 10, 11, 12, and 13, we have exemplified a modification, in which parts similar to parts shown in Figs. 3 to 6 inclusive are identified by similar reference numerals raised to the series 100. I11 this exemplifica tion, the tension-member is anchored to the lower part of the inner end 157 of the over hanging portion of the drill-arm by means of pins 175 received through registering holes in the casting and in one end of the tension-member, the other end of the tensionmember being provided with a threaded socket 176, in which the threaded end of a bolt 177 is received, the inner end of the head 17 8 of the bolt bearing against the inclined face 167 of a lug 164 on the outer end of the drill-arm. The bolt is arranged to rotate in a slanting hole 165 in the outer end of the drill-arm.

hen the proper bending and compressive action upon the cast metal drill-arm and the proper tensile force upon the tension-bar has been provided, the outer end of the tensionbar and the outer end of the drill-arm are preferably connected by anchor-pins 168 received through registering holes in the drillarm and the tension-bar. Upon such assemblage of the parts, the head 178 and the outer end of the bolt 177 and the lug 164 may be removed, and the outer end face of the drillarm provided with a suitable finish to cover the shank of the bolt.

Referring to Figs. 14 and 15 inclusive, which show a further modification, parts similar to the parts shown in Figs. 3 t0 6 'nclusive are identified by similar reference numerals raised to the series 200. In this modification the respective ends of the tension-member 255 are threaded as at 280, 281. The tension-member 255 is shown round and preferably of the same cross-sectional area as the tension-members 55, 155. The respective ends of the tension-member 255 are respectively received through bores 282, 283, in lugs 284, 285, in the diagonally opposite corners 258, 270, in the drill-arm. Nuts 286, 287, are threaded about the respective ends of the rods, being received against slanting end faces 288, 289, of the lugs 284:, 285, respectively at the lower inner end and at the upper outer end of the cast metal drill-arm. These end faces are perpendicular to the axis of the rod.

lVhen the proper compressive action has been had upon the cast metal drill-arm and proper tension applied to the tension-bar, as by applying bending and compressive forces to the cast drill-arm, and by rotating the nuts, the tension-member is preferably anchored at its respective ends, as by anchoring pins 292 at the lower inner corner 258 and by anchor 'ng pins 293 at the upper outer corner 270 of the drill-arm, the pins being received through registering holes in the cast metal drill-arm and the tensionbar.

If desired, the supplementing anchoring pins may be omitted, and the nuts 286, 287,

which may remain complete and in place, be relied on the anchoring means, for the reason that the positions of the nuts and the lugs therefor will in the positions shown be unobjectionable.

After the cast metal drill-arm has been thus operated on, and deflected, and the shape of the drill-arm thus fixed, the drill-arm is provided with the guideways, as 36, 37, 38, 39, 40, along which the tool-slide is arranged to be moved for adjusting the tool to proper position with relation to the work. Distortion of the guideways, which would otherwise result from treating the cast metal drillarm in manner stated, is avoided, and guideways, which are parallel with each other and with the proper plane of movement of the point of the tool in the drill-spindle, and which are in straight lines, are thus assured in the finished drill-arn'i and during operation.

The bearings for shafts, rods and other parts extending longitudinally of the drill arm are also preferably formed after the drill-arm has been treated in accordance with our invention, so that the same may be parallel and in line throughout the length of the drill-arm, and remain so during operation.

The groove 95 for the toothed rack 96, is also cut and the rack inserted in the groove, after the drill-arm has been deflected to absorb the natural flexure of the casting of the drill-arm and fixed in its deflected form in accordance with the teachings of our invention, and other parts may be applied to the drill-arm after such fiexure and fixing. The rack mentioned is the usual rack employed for lateral positioning movements of the drillhead on the drill-arm.

e have explained our invention, and have presented several examples of its embodiment. It will be readily understood that other embodiments of the same may be employed and that changes may be made without departing from the spirit of our invention as contained in the accompanying claims.

Having thus fully described our invention, what we claim as new, and desire to secure by Letters Patent, is:

1. A radial drill-arm for a radial metal drilling machine, said drill-arm comprising a cast body of metal having an upright bearing portion arranged to be received about the upright column of the drilling machine and a laterally extending overhanging armportion, a tension member extending obliquely in said arm-portion of said cast body throughout the greater portion of the length of said arm-portion, and means whereby said tension member is anchored obliquely in a single direction at its respective ends to said cast body, and said cast body between said anchoring means being under compression and said tension member being under tension to resist deflection in said drill-arm.

2. A radial drill-arm for a metal radial drilling machine having an upright post and an upright column thereabout, said drillarm adapted to be adjusted up and down on said upright column and to be radially positioned about said upright post, said drillarm comprising a cast body of metal having an upright bearing portion about said column and a laterally extending arm-portion, a tension member extending obliquely in said arm-portion of said cast body throughout the greater portion of the length of said arm-portion, and means whereby said tension member is anchored under tension at its respective ends to obliquely opposite end portions of said cast body, with said cast body under compression between said obliquely opposite ends, said arm-portion of said drill.- arm under such compression provided with longitudinal guideways for a drill-slide, and said tension member extending obliquely in a vertical plane crosswise of said guideways.

3. A radial drill-arm for a metal radial drilling machine having an upright column, radial drill arm comprising a cast body of metal having a vertical bearing portion and a laterally extending arm-portion, said bearing portion arranged to be received about said upright column and adapted to be ad justed up and down on said column, said armportion provided with a bore extending lengthwise of said arm-portion, a tension member in said bore extending obliquely throughout the greater portion of the length 01 said arm-portion, and means whereby said tension member is anchored at its respective ends to obliquely opposite corners of said arm-portion of said cast body, said drill-arm provided with longitudinal guideways for a drill-slide, said tension member extending in a vertical plane obliquely across the horizontal planes in which said longitudinal guideways are located, and said tension membe acting to resist deflection in said drillarm by upward working stresses upon said drill-arm.

4. A radial drill-arm for a radial drilling machine having an upright column, said; drill-arm comprising a cast body of metal having an upright bearing and an overhanging arm-portion extending laterally from said upright bearing, said upright bearing arranged to be received about said upright column and to be adjusted up and down on said column for adjusting said drill-arm to elevation, said overhanging portion provided with straight laterally extending parallel guideways for a drill-head and a tension member in said overhanging arm-portion eX- tending obliquely crosswise of said gnideways and having one end thereof fixed to said casting adjacent said bearing at one corner of said e erhanging arm-portion and its other end fixed' to s'aid'c asting adjacent a diagonalv r 1, i i i a r 1y opposite corner of the outer end of sand overhanging arm-portion'and resisting bending stresseson said overhangingarm-portion dial drill-arm comprising a cast body of metal v.-

i upright bearing and an overhanging arm-portion, said upright bearing adapted to he received about said upright column and [to be adjusted up and down thereon, said overhanging a r'm-portion provided with longitudinal straight and parallel guideways for a drill-slide provided with complemental parallel gui-deways, and a tension member in said overhanging arm-portion having substantially greater tensile strength than the tensile strength of said cast overhanging armportion and extending in said cast body obliquely to said longitudinal parallel guideways, the respective ends of said tension member fixed under tension to obliquely opposite end portions of said overhanging armportion for maintaining said longitudinal guideways straight and parallel.

6. In a radial drilling machine comprising an upright post and an upright column rotatable thereabout, a drill-arm comprising a cast body of metal having an upright bearing and an overhanging arm-portion extending laterally from said bearing, said upright bearing adapted to be received about said column and arranged to be adjusted up and down on said column, said arm portion provided with straight longitudinal parallel guideways adapted to coordinate with complemental guideways on a drill-slide adapted to be adjusted along said overhanging arm-portion, a tension member having substantially greater tensile strength than the tensile strength of said cast body, said tension member extending obliquely in said overhanging arm-portion of said cast bony, and anchoring means between the respective ends of said tension member and diagonally opposite cornersof said overhanging armportion, said tension member being under abnormal tension and said casting under abnormal compression, the lines of force of said tension and compression being substantially parallel and counter to each other, and said tension member extending obliquel crosswise of said guid-eways for maintain said guideways straight and parallel with each other.

7. A radial drill-arm for a radial drilling machine comprising a cast body of metal having an upright bearing and an overhanging arm-portion extending laterally from said upright bearing, said drill-arm adapted to be adjusted up and down on the upright column or the drilling machine, said overhanging arm-portion provided with straight iii parallel longitudinal guideways for a drillslide, a tension member having tensile resistance substantially greater than the tensile resistance of said cast overhanging arm-portion, said tension member extending in said cast body obliquely to said straight parallel longitudinal guideWays, means exerting tension on said tension member and compression on said cast overhanging arm-portion, and anchoring means between the respective ends of said tension member and diagonally opposite corners of said overhanging arm-portion, and arranged for resisting bending stresses upon said drills-arm by upwardly directed forces under said overhanging arm-portion.

In testimony whereof, We have hereunto signed our names.

ALBERT E. ROBINSON. TVILLIAM L. SGHELLENBAGH. 

